I actually am a bit of a health and running coach during my free time. I operate through the company Herbalife, and have come away with combining some practices with my own running knowledge when it comes to mindset and motivation:
The big key to it all is always consistency. But just as a long distance runner doesn't hurt every single mile of a marathon, you should not kill your mental strength each day to achieve a weight loss goal. If it hurts to a level that you can't think positively after a weeks worth of training, then you could be doing it in a much more efficient way.
Take for example, cardio. Many people believe it is the best exercise to kill fat. Which, being a long distance runner myself, I can say that it is. Cardio burns more calories and fat in hour plus long exercises than any other workout plan you can think of.
However, while it may be the most effective, it actually is not the most efficient. Running and cardio development takes time, a process that you can not faulter on the first few stages or you lose all of the benefit you gained (Running is a snowball effect type of sport). It takes months for people to make it into the position they want to be in for the workouts they need to do before they can even shred the weight they want to.
The alternative I've seen in practice are workouts designed to build muscle. The body recovers based on the nutrition you put in your body, where "bad food" will usually just be food that lacks in substances needed to grow muscle, while also containing high fat. Working out burns some calories, but pounds of fat don't get shredded by the amount of work you do in the gym. Workouts destroy and weaken your muscle: nutrition rebuilds them with the substance you put in your body.
So if you eat foods like McDonald's or other junk items, your body won't recover from workouts very well because most of the substance in fast foods/junk foods is either fat or sugars. You need protien, healthy carbs, vitamins, phytonutrients, etc. to build muscle. This sort of poor nutrition then makes it worse: you destroyed your mind and body, then put poor nutrition to rebuild it. The metaphor I like to compare it to is when you pull all nighters, then sleep for two hours trying to wake up early. You'd have been better off had you not slept at all, just like you would be better off not working out if you don't plan to eat something with good nutritional value in it afterwards.
And once you build muscle, your body burns more fat in utilizing that muscle through your daily routine. By having a stronger body, you end up shredding pounds of fat because your muscles have to draw more from your fat stores just to do everyday tasks. You don't have to be body builder size either: a simple rise in muscle mass for every portion of your body is going to make an impact. You'll have a body that burns more calories if you target every muscle group rather than making one massive. This can also be further expanded on: work out early! Morning workouts kickstart your metabolism, basically "waking up your body". Having your body turned on for more hours of the day = more calories burned than any single workout.
So basic sum up is simple:
-Working out should always have the purpose of building muscle, never burning fat. Knowing that the fat will burn from building stronger muscles makes mentally committing in the long run much easier.
-Proper nutrition is the key to gaining muscle. Workouts only destroy your muscles and teach your body to build them up; what you eat determines if the job the workout teaches your body gets done or not.
-Bigger muscles = more fat shredded. Why try to focus on killing more than 300 calories in a single workout, when you can go from burning a 1,000 calories to 2,000 by having to use bigger muscles to move around?
-You don't need to be massive: it's more efficient to build every muscle slightly than to build a few of them massively. If you slack on one muscle group, then work it out: it'll give you something to do everyday and it'll make things a variety.
And lastly put, eating bad is honestly better than not eating at all. You should consume at least 200-300 calories of something before and after you workout, regardless of what it is. As much as unhealthy foods are terrible for you, you need something to build muscle from and unhealthy foods have some nutrition to them. Very poor nutrition is still better than no nutrition at all.